Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1987-12-15
1988-10-25
Westin, Edward P.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
250557, 356400, 356401, H01L 2130
Patent
active
047806150
ABSTRACT:
An alignment system usable in a semiconductor device manufacturing exposure apparatus for superimposingly transferring a circuit pattern of a reticle onto each of patterns formed on individual portions of a semiconductor wafer, for sequentially aligning the individual portions of the wafer with respect to the reticle by use of alignment marks formed in or on scribe lines defined between the individual portions of the wafer. An optical system for detecting the alignment marks is disposed outside the path of light used for the sake of pattern transfer. In the course of movement of the wafer for bringing a particular shot area to an exposure station, the alignment marks for the particular shot area are photoelectrically detected through the mark detecting optical system and, on the basis of the detection of the alignment marks, the reticle and the wafer are relatively moved into alignment such that, when the particular shot area reaches the exposure station, the pattern of the reticle can be accurately superimposed on the pattern already formed on the particular shot area of the wafer. As a result, TTL (through-the-lens) alignment is assured without degradation of throughput of the exposure apparatus.
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Canon Kabushiki Kaisha
Westin Edward P.
Wieland Charles F.
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